DESIGN AND ANALYSIS OF ALL OPTICAL DIELECTRIC CYLINDRICAL NANOANTENNAS

Abstract

In this thesis, we theoretically demonstrate ultra-directional, azimuthally symmetric forward scattering by dielectric cylindrical nanoantennas for futuristic nanophotonic applications in visible and near-infrared regions. Electric and magnetic dipoles have been optically induced in the nano-cylinders at the resonant wavelengths. It has been demonstrated that the cylindrical dielectric nanoparticles exhibit complete suppression of backward scattering and improved forward scattering at first generalized Kerker’s condition. The influence of gap between nano-cylinder elements on the scattering pattern of the homodimers has been demonstrated. Further, for highly directive applications a linear chain of ultra-directional cylindrical nanoantenna array has been proposed. The effect of the dimensions and material of the dielectric nanocylinder on the scattering properties of the cylindrical nanoantenna has been analyzed using finite element method (FEM). It has been observed that the scattering characteristics of dielectric cylindrical nanoantennas are highly dependent on the dielectric material and aspect ratio of nanocylinder. It has been demonstrated that as dielectric permittivity of the nanocylinder decreases the gap between electric and magnetic resonance decreases hence the directivity increases. We have analyzed that the variation in diameter of nanocylinder has great influence on the strength of interference of electric and magnetic dipolar resonances. As the radius of the nanocylinder is increased, the electric and magnetic dipolar resonances shift towards the higher wavelengths, however no significant change has been observed with the increase in height. Thus, the cylindrical nanoparticles can be used for the design and development of tunable unidirectional nanoantenna applications in visible to near infra-red range.